1. Field of the Invention
The present invention is directed to an interlock arrangement for evaporators in an anesthesia apparatus, the anesthesia apparatus being of the type having at least two evaporators connectable to a gas distributor for setting a desired gas concentration as well as means for preventing more than one evaporator from being activated at a time.
2. Description of the Prior Art and Related Application
An anesthesia apparatus is disclosed in the Swedish Patent No. 507 899 having at least two evaporators for setting a desired gas concentration and a valve belonging to each evaporator, the valve controlling the gas flow through the respective evaporator, as well as means for enabling an opening and a closing of the valves that simultaneously prevent more than one evaporator from being activated. The evaporators and the valves are connectable to a gas distributor.
This anesthesia apparatus is provided with an evaporator carousel forming the gas distributor or the holder for the evaporators and valves and a gas supply unit, the gas distributor being rotatable relative to the gas supply unit. As a result, it is simple for a physician to change position relative to the patient and nonetheless have control over which evaporator is activated and what anesthesia concentration has been set at the active evaporator. As needed, the anesthesiologist can change the concentration of the anesthetic despite changing work positions, by rotating the gas distributor or holder, so that the activated evaporator is in a good position for the change in the concentration that has been set. In order to avoid having more than one evaporator activated at the same time, these applications state that an interlock arrangement is present, but details of such an interlock arrangement are not disclosed in detail in these applications.
U.S. Pat. No. 4,307,718 discloses an interlock arrangement for two evaporators arranged side-by-side in an anesthesia apparatus. Each evaporator has a cylindrical container with a rotary dial thereon as a cover, which is also used for setting the vapor concentration. Each adjustment dial has a recess at the cylindrical peripheral surface thereof. The interlock arrangement is formed by an arm which is pivotable around a shaft, the arm being provided with an outwardly directed pin arranged at each end, and the pins can be brought into engagement with the recesses. When the arm is pivoted into a position in which one pin is in engagement with the recess of one adjustment dial and closes this evaporator, the other evaporator can be set into a desired position, and vice versa. Such an interlock arrangement is exclusively limited to two evaporators.